1. Elements of a Weight of Evidence Determination
Donna Kenski
Midwest RPO
presented at National RPO Meeting,
Denver, June 2005

2. Components Start with integrated conceptual model—O3, PM, RH
Source apportionment of STN and IMPROVE
Organic speciation and source apportionment – urban and rural
Ammonia/nitric acid – which precursors control PM?
PM trends
Episode analysis
Transport and trajectory analysis
Ozone
weekend/weekday differences,
trends,
NOx/VOC limitation

3. Source apportionment of IMPROVE and STN data
Work by Eugene Kim and Phil Hopke: PMF, ME, CPF, PSCF

4. Bondville, IL Bondville IMPROVE site Mar. 2001 – May 2003 9 sources
Source profiles
Bondville IMPROVE site
Mar – May 2003
9 sources

5. Averaged source contributions
Bondville, IL
Averaged source contributions

6. Time-series source contributions Backward trajectories
Bondville, IL
Time-series source contributions
Backward trajectories
4/22/2001
7/1/2002

7. Weekday/weekend variations
Bondville, IL
CPF plots
Weekday/weekend variations

8. 8 carbon fraction profiles
Gasoline emissions include the lower temperature carbon fractions (OC1 - OC4).
Diesel emissions contain large amounts of the EC1
Gasoline vehicle emissions
Diesel emissions

9. Secondary sulfate aerosol: Bondville
Summer-high: Tennessee, Ohio river valley, Ohio, Louisiana, Alabama
Carbon-high: Canadian forest fire, Nebraska, Dakota, Minnesota, Iowa
Winter-high: Nebraska, Kansas, Oklahoma, Texas, Tennessee valley, Ohio river valley

10. Inter-site comparison
General summary of the source contributions
Secondary sulfate
The largest contribution to the PM2.5
Secondary nitrate, Motor vehicle
The 2nd largest contribution to the PM2.5

11. Gasoline vehicle emissions
No strong weekday/weekend variation
Rural sites show lower conc.

12. LADCO Organic Speciation Projects
1. Seney National Wildlife Refuge
Analysis of existing speciation carbon channel filters (monthly composites) for 2002
Collection and analysis of 28 high volume filters for summer 2002
2. Urban organics
Collection and analysis of 1/6 day, high volume samples at Indianapolis, Detroit, Cincinnati, Chicago, St. Louis, and Bondville, 2004 calendar year

13. Primary emission tracers

16. Urban organic speciation sites
Detroit, MI
Northbrook, IL
Cincinnati, OH
Bondville, IL
Indianapolis, IN
St. Louis, MO

17. Data Overview
At six sites (five urban, one rural) during Dec 2003 – Feb 2005, collocated with STN measurements, quartz fiber filters (QFFs) sampled
QFFs analyzed for OC/EC
Monthly composites of QFFs for speciation done at all sites
Indianapolis selected for organic speciation of all 60+ samples during period
At Indianapolis and Bondville, 3-hr DRUM data taken during sampling days

18. Seasonal Composition - Indianapolis
Median
OMC>SO4
NO3>OMC>SO4
OC graphed as OMC=1.4*OC

19. Weekday-weekend: OC OC has no significant trend
Northbrook – Feb 04 – Jan 05
Cincinnati – Feb 04 – Jan 05

20. Weekday-weekend: EC EC shows clear weekday-weekend trend
Detroit – Feb 04 – Jan 05
Cincinnati – Feb 04 – Jan 05

21. Urban OC Summary
A large, generally high-quality data set is being assembled
PM2.5 concentrations were sufficiently high and variable during the sampling campaign to be of interest to policy makers
While STN, IMPROVE and other data routinely collected are useful, additional OCEC and speciated organics data will greatly help source apportionment efforts

22. Midwest Ammonia Monitoring
Despite importance of ammonia in atmospheric chemistry, no national studies or routine monitoring of ambient (non-source-influenced) concentrations has been done
To fill data gap, MRPO and CENRAP began rural monitoring in Oct. 2003
Beginning network--10 sites: 9 rural, 1 urban
Current network – 12 sites, 8 rural, 3 urban
All rural sites are IMPROVE sites except Pleasant Green, MO
Denuder/filterpack sampling
Phosphoric acid coated denuder for NH3
Sodium carbonate coated denuder for HNO3 and SO2
Teflon filter followed by nylon filter (for nitrate dissociation)
Two sites (Pleasant Green MO, Lake Sugema IA) use automated R&P samplers (different denuder/inlet configurations)
1/6 day sampling
Two continuous samplers, Pranalytica and IC, at Bondville for QA
Both NH3 and HNO3 very difficult to measure, due to reactivity, ‘stickiness’, low ambient concentrations, significant inlet losses
Too soon to compare with IMPROVE – no data for IMPROVE posted yet for this period
Goals: Characterize rural ambient NH3 (and related parameters) because very few data exist. Need spatial variability, temporal variability (seasonal, diurnal), and relationship of NH3, HNO3 with other gases and PM species.

23. LADCO-CENRAP NH3 Network
Red=urban sites
Blue=rural sites

24. Temporal variation in NH3
Log scale
Base F2 NH3 Emissions

25. Spatial variation in NH3

26. Predicted PM2.5 Concentrations
(Blanchard & Tanenbaum)
At current NH3, PM is about equally sensitive to reductions in SO4 and NO3
At current SO4 level, PM is slightly more sensitive to NH3 reductions than to HNO3 (at this site; sites further west are more sensitive to HNO3 reductions); 30% reduction in NO3 leads to .75 ug less pm, 30% reduction in NH3 leads to 1 ug less PM
PM is about equally sensitive to reductions in SO4 and NO3
PM is slightly more sensitive to NH3 reductions than to HNO3

27. Sample-by-sample evaluation of gas ratio and excess ammonia
Nitric acid limited
Nitric acid limited
Sample-by-sample evaluation of gas ratio and excess ammonia
(Blanchard & Tanenbaum)
Nitric acid limited
Nitric acid limited

28. Preliminary Conclusions
At current conditions, PM mass decreases in response to reductions in sulfate, nitric acid, and ammonia
At current conditions, particulate nitrate formation limited generally by nitric acid
At expected future conditions (i.e., lower sulfate), PM mass is more responsive to nitric acid reductions
Daily and hourly data support same conclusions

29. Future Applications for NH3 Data
Model evaluation (Kirk Baker dissertation)
Inventory validation – daily variability, seasonal variability, diurnal variability
Correlations with meteorology, other AQ parameters
PM episode analysis – Feb. ’05 event, role of snow as source/sink

30. PM Trends

31. Seasonal Urban Trends

32. Weekday/Weekend Ozone Differences (Blanchard&Tanenbaum)

33. Trajectories, Transport

34. Episode Analysis Based on AIRNOW
From Rudy Husar
Time pattern of the 0502 Event
The overall event lasted about 10 days, Jan 28-February 7
The Upper Midwest peaked first (Jan 31-Feb 2); Industrial MW later (Feb 3 – 6)
The Industrial MW region show more diurnal variation (lowest in the mid-afternoon)
0502 PM Event
PM Event

35. 24 hr Average PM-2.5 Concentrations in Michigan (1/26/05 thru 2/10/05)
warm air advection
cold front approaches
From Neal Conatser, Mich. DEQ
strong cold front passes
weak cold front passes